Signal multiplexing apparatus using layered division multiplexing and signal multiplexing method

ABSTRACT

An apparatus and method for multiplexing signals using layered division multiplexing are disclosed. A signal multiplexing apparatus according to an embodiment of the present invention includes a combiner configured to combine a core layer signal and an enhanced layer signal at different power levels to generate a multiplexed signal, a power normalizer configured to reduce power of the multiplexed signal to power corresponding to the core layer signal, and a time interleaver configured to perform interleaving applied to both the core layer signal and the enhanced layer signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/515,760 filed Jul. 18, 2019, which is a continuation of U.S.patent application Ser. No. 16/182,419 filed Nov. 6, 2018, which is acontinuation of U.S. patent application Ser. No. 15/124,646 filed Sep.8, 2016, now U.S. Pat. No. 10,164,740, which is a U.S. National Stage ofInternational Patent Application No. PCT/KR2015/001832 filed Feb. 25,2015, which claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0055860 and 10-2015-0026288 filed in the KoreanIntellectual Property Office on May 9, 2014 and Feb. 25, 2015,respectively, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to broadcast signal transmission/receptiontechnology adapted for use in a broadcasting system and, moreparticularly, to a broadcast signal transmission/reception system thatmultiplexes/demultiplexes and then transmits/receives two or moresignals.

BACKGROUND ART

Bit-Interleaved Coded Modulation (BICM) is bandwidth-efficienttransmission technology, and is implemented in such a manner that anerror-correction coder, a bit-by-bit interleaver and a high-ordermodulator are combined with one another.

BICM can provide excellent performance using a simple structure becauseit uses a low-density parity check (LDPC) coder or a Turbo coder as theerror-correction coder. Furthermore, BICM can provide high-levelflexibility because it can select modulation order and the length andcode rate of an error correction code in various forms. Due to theseadvantages, BICM has been used in broadcasting standards, such as DVB-T2and DVB-NGH, and has a strong possibility of being used in othernext-generation broadcasting systems.

In general, in order to multiplex signals, Time Division Multiplexing(TDM) or Frequency Division Multiplexing (FDM) is widely used. Recently,there is an urgent need for new multiplexing technology that isapplicable to a next generation broadcasting system and provides greaterflexibility and performance than TDM and FDM.

DISCLOSURE Technical Problem

An object of the present invention is to provide a new signalmultiplexing technology that is capable of providing greater flexibilityand performance than TDM and FDM.

Another object of the present invention is to efficientlymultiplex/demultiplex signals corresponding to two or more layers bycombining the signals at different respective power levels.

Technical Solution

In order to accomplish the above objects, the present invention providesa signal multiplexing apparatus, including: a combiner configured tocombine a core layer signal and an enhanced layer signal at differentpower levels to generate a multiplexed signal; a power normalizerconfigured to reduce power of the multiplexed signal to powercorresponding to the core layer signal; and a time interleaverconfigured to perform interleaving applied to both the core layer signaland the enhanced layer signal.

In this case, the signal multiplexing apparatus may further include aninjection level controller configured to generate a power-reducedenhanced layer signal by reducing the power of the enhanced layersignal; and the combiner may generate the multiplexed signal bycombining the core layer signal and the power-reduced enhanced layersignal.

In this case, the signal multiplexing apparatus may further include: acore layer Bit-Interleaved Coded Modulation (BICM) unit configured tocorrespond to the core layer signal; and an enhanced layer BICM unitconfigured to perform Bit-Interleaved Coded Modulation (BICM) encodingdifferent from that of the core layer BICM unit.

In this case, the core layer BICM unit may have a lower bit rate thanthe enhanced layer BICM unit, and may be more robust than the enhancedlayer BICM unit.

In this case, the power normalizer may correspond to a normalizingfactor, and may reduce the power of the multiplexed signal by an amountby which the power has been increased by the combiner.

In this case, the injection level controller may correspond to a scalingfactor; each of the normalizing factor and the scaling factor may be avalue that is larger than 0 and smaller than 1; the scaling factor maydecrease as a reduction in power corresponding to the injection levelcontroller becomes larger; and the normalizing factor may increase as areduction in power corresponding to the injection level controllerbecomes larger.

In this case, the injection level controller may change an injectionlevel between 3.0 dB and 10.0 dB in steps of 0.5 dB.

In this case, the enhanced layer signal may correspond to enhanced layerdata that is restored based on cancellation corresponding to therestoration of core layer data corresponding to the core layer signal.

In this case, the core layer BICM unit may include: a core layer errorcorrection encoder configured to perform error correction encoding onthe core layer data; a core layer bit interleaver configured to performbit interleaving corresponding to the core layer data; and a core layersymbol mapper configured to perform modulation corresponding to the corelayer data.

In this case, the enhanced layer BICM unit may include: an enhancedlayer error correction encoder configured to perform error correctionencoding on the enhanced layer data; an enhanced layer bit interleaverconfigured to perform bit interleaving corresponding to the enhancedlayer data; and an enhanced layer symbol mapper configured to performmodulation corresponding to the enhanced layer data.

In this case, the enhanced layer error correction encoder may have ahigher bit rate than the core layer error correction encoder; and theenhanced layer symbol mapper may be less robust than the core layersymbol mapper.

In this case, the combiner may combine one or more extension layersignals, having lower power levels than the core layer signal and theenhanced layer signal, with the core layer signal and the enhanced layersignal.

An embodiment of the present invention provides a signal multiplexingmethod, including: combining a core layer signal and an enhanced layersignal at different power levels to generate a multiplexed signal;reducing power of the multiplexed signal to power corresponding to thecore layer signal; and performing interleaving applied to both the corelayer signal and the enhanced layer signal.

In this case, the signal multiplexing method may further includegenerating a power-reduced enhanced layer signal by reducing the powerof the enhanced layer signal; and the combining may include generatingthe multiplexed signal by combining the core layer signal and thepower-reduced enhanced layer signal.

In this case, the reducing power of the multiplexed signal may includereducing the power of the multiplexed signal by an amount by which thepower has been increased by the combining.

In this case, the generating a power-reduced enhanced layer signal mayinclude changing an injection level between 3.0 dB and 10.0 dB in stepsof 0.5 dB.

In this case, the combining may include combining one or more extensionlayer signals, having lower power levels than the core layer signal andthe enhanced layer signal, with the core layer signal and the enhancedlayer signal.

Advantageous Effects

According to the present invention, a new signal multiplexing technologythat is capable of providing greater flexibility and performance thanTDM and FDM is provided.

Furthermore, according to the present invention, signals correspondingto two or more layers can be efficiently multiplexed/demultiplexed bycombining the signals at different respective power levels.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a broadcast signaltransmission/reception system according to an embodiment of the presentinvention;

FIG. 2 is an operation flowchart illustrating a broadcast signaltransmission/reception method according to an embodiment of the presentinvention;

FIG. 3 is a block diagram illustrating an example of the signalmultiplexer illustrated in FIG. 1;

FIG. 4 is a block diagram illustrating another example of the signalmultiplexer illustrated in FIG. 1;

FIG. 5 is a block diagram illustrating an example of the signaldemultiplexer illustrated in FIG. 1;

FIG. 6 is a block diagram illustrating another example of the signaldemultiplexer illustrated in FIG. 1;

FIG. 7 is a diagram showing an increase in power attributable to thecombination of a core layer signal and an enhanced layer signal;

FIG. 8 is a block diagram illustrating another example of the signalmultiplexer illustrated in FIG. 1;

FIG. 9 is a block diagram illustrating still another example of thesignal multiplexer illustrated in FIG. 1;

FIG. 10 is a block diagram illustrating still another example of thesignal demultiplexer illustrated in FIG. 1;

FIG. 11 is a block diagram illustrating still another example of thesignal demultiplexer illustrated in FIG. 1; and

FIG. 12 is an operation flowchart illustrating a signal multiplexingmethod according to an embodiment of the present invention.

MODE FOR INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the accompanying drawings. Redundant descriptions anddescriptions of well-known functions and configurations that have beendeemed to make the gist of the present invention unnecessarily obscurewill be omitted below. The embodiments of the present invention areintended to fully describe the present invention to persons havingordinary knowledge in the art to which the present invention pertains.Accordingly, the shapes, sizes, etc. of components in the drawings maybe exaggerated to make the description obvious.

Preferred embodiments according to the present invention are describedin detail with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating a broadcast signaltransmission/reception system according to an embodiment of the presentinvention.

Referring to FIG. 1, a broadcast signal transmission/reception systemaccording to an embodiment of the present invention includes a broadcastsignal transmission apparatus 110, a wireless channel 120, and abroadcast signal reception apparatus 130.

The broadcast signal transmission apparatus 110 includes a signalmultiplexer 111 for multiplexing core layer data and enhanced layerdata, and an OFDM transmitter 113.

The signal multiplexer 111 combines a core layer signal corresponding tocore layer data and an enhanced layer signal corresponding to enhancedlayer data at different power levels, and generates a multiplexed signalby performing interleaving applied to both the core layer signal and theenhanced layer signal.

The OFDM transmitter 113 transmits the multiplexed signal using an OFDMcommunication method via an antenna 117, thereby allowing thetransmitted OFDM signal to be received via the antenna 137 of thebroadcast signal reception apparatus 130 over the wireless channel 120.

The broadcast signal reception apparatus 130 includes an OFDM receiver133 and a signal demultiplexer 131. When the signal transmitted over thewireless channel 120 is received via the antenna 137, the OFDM receiver133 receives an OFDM signal through synchronization, channel estimation,and equalization.

The signal demultiplexer 131 restores the core layer data from thesignal received via the OFDM receiver 133 first, and then restores theenhanced layer data via cancellation corresponding to the restored corelayer data.

Although not explicitly illustrated in FIG. 1, broadcast signaltransmission/reception system according to an embodiment of the presentinvention may multiplex/demultiplex one or more pieces of extensionlayer data in addition to the core layer data and the enhanced layerdata. In this case, the extension layer data may be multiplexed at apower level lower than that of the core layer data and the enhancedlayer data. Furthermore, when two or more extension layers are included,the injection power level of a second extension layer may be lower thanthe injection power level of a first extension layer, and the injectionpower level of a third extension layer may be lower than the injectionpower level of the second extension layer.

FIG. 2 is an operation flowchart illustrating a broadcast signaltransmission/reception method according to an embodiment of the presentinvention.

Referring to FIG. 2, in the broadcast signal transmission/receptionmethod according to the present embodiment, a core layer signal and anenhanced layer signal are combined at different power levels tomultiplex the signals at step S210.

Furthermore, in the broadcast signal transmission/reception methodaccording to the present embodiment, the multiplexed signal is OFDMtransmitted at step S220.

Furthermore, in the broadcast signal transmission/reception methodaccording to the present embodiment, the transmitted signal is OFDMreceived at step S230.

In this case, at step S230, synchronization, channel estimation andequalization may be performed.

Furthermore, in the broadcast signal transmission/reception methodaccording to the present embodiment, core layer data is restored fromthe received signal at step S240.

Furthermore, in the broadcast signal transmission/reception methodaccording to the present embodiment, enhanced layer data is restoredthrough the cancellation of the core layer signal at step S250.

In particular, steps S240 and S250 illustrated in FIG. 2 may correspondto demultiplexing operations corresponding to step S210.

FIG. 3 is a block diagram illustrating an example of the signalmultiplexer illustrated in FIG. 1.

Referring to FIG. 3, a signal multiplexer according to an embodiment ofthe present invention may include a core layer Bit-Interleaved CodedModulation (BICM) unit 310, an enhanced layer BICM unit 320, aninjection level controller 330, a combiner 340, and a time interleaver350.

Generally, a Bit-Interleaved Coded Modulation (BICM) device includes anerror correction encoder, a bit interleaver, and a symbol mapper. Eachof the core layer BICM unit 310 and the enhanced layer BICM unit 320illustrated in FIG. 3 may include an error correction encoder, a bitinterleaver, and a symbol mapper.

As illustrated in FIG. 3, core layer data and enhanced layer data passesthrough different respective BICM units, and are then combined by thecombiner 340.

That is, the core layer data passes through the core layer BICM unit310, the enhanced layer data passes through the enhanced layer BICM unit320 and then the injection level controller 330, and the core layer dataand the enhanced layer data are combined by the combiner 340. In thiscase, the enhanced layer BICM unit 320 may perform BICM encodingdifferent from that of the core layer BICM unit 310. That is, theenhanced layer BICM unit 320 may perform higher bit rate errorcorrection encoding or symbol mapping than the core layer BICM unit 310.Furthermore, the enhanced layer BICM unit 320 may perform less robusterror correction encoding or symbol mapping than the core layer BICMunit 310.

For example, the core layer error correction encoder may exhibit a lowerbit rate than the enhanced layer error correction encoder. In this case,the enhanced layer symbol mapper may be less robust than the core layersymbol mapper.

The combiner 340 may be viewed as functioning to combine the core layersignal and the enhanced layer signal at different power levels.

The core layer data uses forward error correction (FEC) code having alow code rate in order to perform robust reception, while the enhancedlayer data uses FEC code having a high code rate in order to achieve ahigh data transmission rate.

That is, the core layer data may have a broader coverage than theenhanced layer data in the same reception environment.

The enhanced layer data having passed through the enhanced layer BICMunit 320 is adjusted in gain (or power) by the injection levelcontroller 330, and is combined with the core layer data by the combiner340.

That is, the injection level controller 330 generates a power-reducedenhanced layer signal by reducing the power of the enhanced layersignal.

In this case, the combiner 340 may be viewed as generating a multiplexedsignal by combining the core layer signal with the power-reducedenhanced layer signal.

The data obtained through the combination of the combiner 340 passesthrough the time interleaver 350 for distributing burst errors occurringover a channel, and is transmitted via the OFDM transmitter robust tomulti-path and Doppler phenomena.

In this case, it can be seen that the time interleaver 350 performsinterleaving that is applied to both the core layer signal and theenhanced layer signal. That is, the core layer and the enhanced layershare the time interleaver, thereby preventing the unnecessary use ofmemory and also reducing latency at the receiver.

Although will be described later in greater detail, the enhanced layersignal may correspond to enhanced layer data restored based oncancellation corresponding to the restoration of core layer datacorresponding to the core layer signal.

FIG. 4 is a block diagram illustrating another example of the signalmultiplexer illustrated in FIG. 1.

Referring to FIG. 4, it can be seen that a signal multiplexermultiplexes data corresponding to N (N is a natural number equal to orlarger than 1) extension layers together in addition to core layer dataand enhanced layer data.

That is, the signal multiplexer illustrated in FIG. 4 includes Nextension layer BICM units 410, . . . , 430 and injection levelcontrollers 440, . . . , 460 in addition to a core layer BICM unit 310,an enhanced layer BICM unit 320, an injection level controller 330, acombiner 340, and a time interleaver 350.

The core layer BICM unit 310, enhanced layer BICM unit 320, injectionlevel controller 330, combiner 340 and time interleaver 350 illustratedin FIG. 4 have been described in detail in conjunction with FIG. 3.

Each of the N extension layer BICM units 410, . . . , 430 independentlyperforms BICM encoding, and each of the injection level controllers 440,. . . , 460 performs power reduction corresponding to a correspondingextension layer, thereby enabling a power reduced extension layer signalto be combined with other layer signals via the combiner 340.

In particular, it is preferred that a reduction in power correspondingto each of the injection level controllers 440, . . . , 460 be higherthan a reduction in power of the injection level controller 330. Thatis, a lower one of the injection level controllers 330, 440, . . . , 460illustrated in FIG. 4 may correspond to a larger reduction in power.

In the present invention, power adjustment may be increasing ordecreasing the power of an input signal, and may be increasing ordecreasing the gain of an input signal.

The time interleaver 350 performs interleaving equally applied to thesignals of the layers by interleaving the signals combined by thecombiner 340.

FIG. 5 is a block diagram illustrating an example of the signaldemultiplexer illustrated in FIG. 1.

Referring to FIG. 5, a signal demultiplexer according to an embodimentof the present invention includes a time deinterleaver 510, a core layerBICM decoder 520, an enhanced layer symbol extractor 530, and anenhanced layer BICM decoder 540.

In this case, the signal demultiplexer illustrated in FIG. 5 maycorrespond to the signal multiplexer illustrated in FIG. 3.

The time deinterleaver 510 receives a received signal from an OFDMreceiver for performing operations, such as synchronization, channelestimation and equalization, and performs an operation related to thedistribution of burst errors occurring over a channel.

The output of the time deinterleaver 510 is provided to the core layerBICM decoder 520, and the core layer BICM decoder 520 restores corelayer data.

In this case, the core layer BICM decoder 520 includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder. The core layer symbol demapper calculatesLog-Likelihood Ratio (LLR) values related to symbols, the core layer bitdeinterleaver strongly mixes the calculated LLR values with bursterrors, and the core layer error correction decoder corrects erroroccurring over a channel.

In particular, the core layer error correction decoder may output onlyinformation bits, or may output whole bits in which information bitshave been mixed with parity bits. In this case, the core layer errorcorrection decoder may output only information bits as core layer data,and may output whole bits in which information bits have been mixed withparity bits to the enhanced layer symbol extractor 530.

The enhanced layer symbol extractor 530 is provided with the whole bitsby the core layer BICM decoder 520 of the core layer error correctiondecoder, and extracts enhanced layer symbols from the output signal ofthe time deinterleaver 510.

In this case, the enhanced layer symbol extractor 530 includes a buffer,a subtracter, a core layer symbol mapper, and a core layer bitinterleaver. The buffer stores the output signal of the timedeinterleaver 510. The core layer bit interleaver receives the wholebits (information bits+parity bits) of the core layer BICM decoder, andperforms the same core layer bit interleaving as the transmitter. Thecore layer symbol mapper generates core layer symbols, which are thesame as the transmitter, from the interleaved signal. The subtracterobtains enhanced layer symbols by subtracting the output signal of thecore layer symbol mapper from the signal stored in the buffer, andtransfers the enhanced layer symbols to the enhanced layer BICM decoder540.

In this case, the core layer bit interleaver and core layer symbolmapper included in the enhanced layer symbol extractor 530 may be thesame as the core layer bit interleaver and the core layer symbol mapperillustrated in FIG. 3.

The enhanced layer BICM decoder 540 receives the enhanced layer symbols,and restores enhanced layer data.

In this case, the enhanced layer BICM decoder 540 may include anenhanced layer symbol demapper, an enhanced layer bit deinterleaver, andan enhanced layer error correction decoder. The enhanced layer symboldemapper calculates Log-Likelihood Ratio (LLR) values related to theenhanced layer symbols, the enhanced layer bit deinterleaver stronglymixes the calculated LLR values with burst errors, and the enhancedlayer error correction decoder corrects error occurring over a channel.

That is, the signal demultiplexer illustrated in FIG. 5 restores corelayer data first, leaves only enhanced layer symbols by cancellationcore layer symbols in the received signal symbols, and then restoresenhanced layer data. Since signals corresponding to respective layersare combined at different power levels, as described in conjunction withFIGS. 3 and 4, data restoration having the lowest error is achieved onlywhen the restoration starts with the signal combined at the highestpower level.

FIG. 6 is a block diagram illustrating another example of the signaldemultiplexer illustrated in FIG. 1.

Referring to FIG. 6, a signal demultiplexer according to an embodimentof the present invention includes a time deinterleaver 510, a core layerBICM decoder 520, an enhanced layer symbol extractor 530, an enhancedlayer BICM decoder 540, one or more extension layer symbol extractors650 and 670, and one or more extension layer BICM decoders 660 and 680.

In this case, the signal demultiplexer illustrated in FIG. 6 maycorrespond to the signal multiplexer illustrated in FIG. 4.

The time deinterleaver 510 receives the received signal from the OFDMreceiver that performs operations, such as synchronization, channelestimation and equalization, and performs the operation of distributingburst errors occurring over a channel.

The output of the time deinterleaver 510 is provided to the core layerBICM decoder 520, and the core layer BICM decoder 520 restores corelayer data.

In this case, the core layer BICM decoder 520 includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder. The core layer symbol demapper calculates LLR valuesrelated to symbols, the core layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the core layer errorcorrection decoder corrects error occurring over a channel.

In particular, the core layer error correction decoder may output onlyinformation bits, or may output whole bits in which information bitshave been combined with parity bits. In this case, the core layer errorcorrection decoder may output only information bits as core layer data,and may output whole bits in which information bits have been mixed withparity bits to the enhanced layer symbol extractor 530.

The enhanced layer symbol extractor 530 receives whole bits from thecore layer error correction decoder of the core layer BICM decoder 520,and extracts enhanced layer symbols from the output signal of the timedeinterleaver 510.

In this case, the enhanced layer symbol extractor 530 includes a buffer,a subtracter, a core layer symbol mapper, and a core layer bitinterleaver. The buffer stores the output signal of the timedeinterleaver 510. The core layer bit interleaver receives whole bits(information bits+parity bits) of the core layer BICM decoder, andperforms core layer bit interleaving that is the same as that of thetransmitter. The core layer symbol mapper generates core layer symbolsthat are the same as those of the transmitter from the interleavedsignal. The subtracter obtains enhanced layer symbols by subtracting theoutput signal of the core layer symbol mapper from the signal stored inthe buffer, and transfers the enhanced layer symbols to the enhancedlayer BICM decoder 540.

In this case, the core layer bit interleaver and the core layer symbolmapper included in the enhanced layer symbol extractor 530 may be thesame as the core layer bit interleaver and the core layer symbol mapperillustrated in FIG. 4.

The enhanced layer BICM decoder 540 receives enhanced layer symbols, andrestores enhanced layer data.

In this case, the enhanced layer BICM decoder 540 may include anenhanced layer symbol demapper, an enhanced layer bit deinterleaver, andan enhanced layer error correction decoder. The enhanced layer symboldemapper calculates LLR values related to the enhanced layer symbols,the enhanced layer bit deinterleaver strongly mixes the calculated LLRvalues with burst errors, and the enhanced layer error correctiondecoder corrects error occurring over a channel.

In particular, the enhanced layer error correction decoder may outputonly information bits, and may output whole bits in which informationbits have been combined with parity bits. In this case, the enhancedlayer error correction decoder may output only information bits asenhanced layer data, and may output whole bits in which information bitshave been mixed with parity bits to the extension layer symbol extractor650.

The extension layer symbol extractor 650 receives whole bits from theenhanced layer error correction decoder of the enhanced layer BICMdecoder 540, and extracts extension layer symbols from the output signalof the subtracter of the enhanced layer symbol extractor 530.

In this case, the extension layer symbol extractor 650 includes abuffer, a subtracter, an enhanced layer symbol mapper, and an enhancedlayer bit interleaver. The buffer stores the output signal of thesubtracter of the enhanced layer symbol extractor. The enhanced layerbit interleaver receives the whole bits information (bits+parity bits)of the enhanced layer BICM decoder, and performs enhanced layer bitinterleaving that is the same as that of the transmitter. The enhancedlayer symbol mapper generates enhanced layer symbols, which are the sameas those of the transmitter, from the interleaved signal. The subtracterobtains extension layer symbols by subtracting the output signal of theenhanced layer symbol mapper from the signal stored in the buffer, andtransfers the extension layer symbols to the extension layer BICMdecoder 660.

In this case, the enhanced layer bit interleaver and the enhanced layersymbol mapper included in the extension layer symbol extractor 650 arethe same as the enhanced layer bit interleaver and the enhanced layersymbol mapper illustrated in FIG. 4.

The extension layer BICM decoder 660 receives the extension layersymbols, and restores extension layer data.

In this case, the extension layer BICM decoder 660 may include anextension layer symbol demapper, an extension layer bit deinterleaver,and an extension layer error correction decoder. The extension layersymbol demapper calculates LLR values related to the extension layersymbols, the extension layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the extension layer errorcorrection decoder corrects error occurring over a channel.

In particular, each of the extension layer symbol extractor and theextension layer BICM decoder may include two or more extractors ordecoders if the extension layers are two or more in number.

That is, in the example illustrated in FIG. 6, the extension layer errorcorrection decoder of the extension layer BICM decoder 660 may outputonly information bits, and may output whole bits in which informationbits have been combined with parity bits. In this case, the extensionlayer error correction decoder outputs only information bits asextension layer data, and may output whole bits in which informationbits have been mixed with parity bits to the subsequent extension layersymbol extractor 670.

The configuration and operation of the extension layer symbol extractor670 and the extension layer BICM decoder 680 can be easily understoodfrom the configuration and operation of the above-described extensionlayer symbol extractor 650 and extension layer BICM decoder 660.

It can be seen that the signal demultiplexer illustrated in FIG. 6restores core layer data first, restores enhanced layer data using thecancellation of core layer symbols, and restores extension layer datausing the cancellation of enhanced layer symbols. Two or more extensionlayers may be provided, in which case restoration starts with anextension layer combined at a higher power level.

Since the signal multiplexer illustrated in FIGS. 3 and 4 is configuredsuch that two or more signals are combined at different power levels, itmay be necessary to adjust the power levels after combination. That is,when a core layer signal and an enhanced layer signal are combined by acombiner, the power level of an obtained multiplexing signal may behigher than that of the core layer signal or enhanced layer signalbefore the combination, and thus a problem, such as the distortion of asignal, attributable to such an increase in power may occur duringsignal transmission/reception.

FIG. 7 is a diagram showing an increase in power attributable to thecombination of a core layer signal and an enhanced layer signal.

Referring to FIG. 7, it can be seen that when a multiplexed signal isgenerated by combining a core layer signal with an enhanced layer signalpower reduced by an injection level, the power level of the multiplexedsignal is higher than that of the core layer signal or enhanced layersignal.

In this case, the injection level adjusted by the injection levelcontroller illustrated in FIG. 3 or 4 may be adjusted from 3.0 dB to10.0 dB in steps of 0.5 dB. When the injection level is 3.0 dB, thepower of the enhanced layer signal is lower than that of the core layersignal by 3 dB. When the injection level is 10.0 dB, the power of theenhanced layer signal is lower than the power of the core layer signalby 10 dB. This relationship is applied not only between the core layersignal and the enhanced layer signal but also between the enhanced layersignal and the extension layer signal or between the extension layersignals.

FIG. 8 is a block diagram illustrating another example of the signalmultiplexer illustrated in FIG. 1.

Referring to FIG. 8, a signal multiplexer according to an embodiment ofthe present invention may include a core layer BICM unit 310, anenhanced layer BICM unit 320, an injection level controller 330, acombiner 340, a power normalizer 810, and a time interleaver 350.

Generally, a BICM device includes an error correction encoder, a bitinterleaver, and a symbol mapper. Each of the core layer BICM unit 310and the enhanced layer BICM unit 320 illustrated in FIG. 8 may includean error correction encoder, a bit interleaver, and a symbol mapper.

As illustrated in FIG. 8, core layer data and enhanced layer data passesthrough different respective BICM units, and are then combined by thecombiner 340.

That is, the core layer data passes through the core layer BICM unit310, the enhanced layer data passes through the enhanced layer BICM unit320 and then the injection level controller 330, and the core layer dataand the enhanced layer data are combined by the combiner 340. In thiscase, the enhanced layer BICM unit 320 may perform BICM encodingdifferent from that of the core layer BICM unit 310. That is, theenhanced layer BICM unit 320 may perform higher bit rate errorcorrection encoding or symbol mapping than the core layer BICM unit 310.Furthermore, the enhanced layer BICM unit 320 may perform less robusterror correction encoding or symbol mapping than the core layer BICM 310unit.

For example, the core layer error correction encoder may exhibit a lowerbit rate than the enhanced layer error correction encoder. In this case,the enhanced layer symbol mapper may be less robust than the core layersymbol mapper.

The combiner 340 may be viewed as functioning to combine the core layersignal and the enhanced layer signal at different power levels.

The core layer data uses forward error correction (FEC) code having alow code rate in order to perform robust reception, while the enhancedlayer data uses FEC code having a high code rate in order to achieve ahigh data transmission rate.

That is, the core layer data may have a broader coverage than theenhanced layer data in the same reception environment.

The enhanced layer data having passed through the enhanced layer BICMunit 320 is adjusted in gain (or power) by the injection levelcontroller 330, and is combined with the core layer data by the combiner340.

That is, the injection level controller 330 generates a power-reducedenhanced layer signal by reducing the power of the enhanced layersignal.

In this case, the injection level controller 330 may control theinjection level from 3.0 dB to 10.0 dB in steps of 0.5 dB.

In this case, the combiner 340 may be viewed as generating a multiplexedsignal by combining the core layer signal with the power-reducedenhanced layer signal.

The signal obtained by the combination of the combiner 340 is providedto the power normalizer 810 so that the power of the signal can bereduced by an increase in power caused by the combination of the corelayer signal and the enhanced layer signal, and then power adjustment isperformed. That is, the power normalizer 810 reduces the power of thesignal, obtained by the multiplexing of the combiner 340, to a powerlevel corresponding to the core layer signal. Since the level of thecombined signal is higher than the level of one layer signal, the powernormalizing of the power normalizer 810 is required in order to preventamplitude clipping, etc. in the remaining portion of a broadcast signaltransmission/reception system.

Assuming that the power levels of the core layer signal and the enhancedlayer signal are normalized to 1 when an enhanced layer signal S_(E) isinjected into a core layer signal S_(C) at a preset injection level, acombined signal may be expressed by S_(C)+αS_(E).

In this case, α is scaling factors corresponding to various injectionlevels. That is, the injection level controller 330 may correspond tothe scaling factor.

For example, when the injection level of an enhanced layer is 3 dB, acombined signal may be expressed by

$S_{C} + {\sqrt{\frac{1}{2}}{S_{E}.}}$

Since the power of a combined signal (a multiplexed signal) increasescompared to a core layer signal, the power normalizer 810 needs tomitigate the increase in power.

The output of the power normalizer 810 may be expressed byβ(S_(C)+αS_(E)).

In this case, β is normalizing factors based on various injection levelsof the enhanced layer.

When the injection level of the enhanced layer is 3 dB, the power of thecombined signal is increased by 50% compared to that of the core layersignal. Accordingly, the output of the power normalizer 810 may beexpressed by

$\sqrt{\frac{2}{3}}{( {S_{C} + {\sqrt{\frac{1}{2}}S_{E}}} ).}$

Table 1 below lists scaling factors α and normalizing factors β forvarious injection levels (CL: Core Layer, EL: Enhanced Layer):

TABLE 1 EL Injection level Scaling Normalizing relative to CL factor αfactor β 3.0 dB 0.7079458 0.8161736 3.5 dB 0.6683439 0.8314061 4.0 dB0.6309573 0.8457262 4.5 dB 0.5956621 0.8591327 5.0 dB 0.56234130.8716346 5.5 dB 0.5308844 0.8832495 6.0 dB 0.5011872 0.8940022 6.5 dB0.4731513 0.9039241 7.0 dB 0.4466836 0.9130512 7.5 dB 0.42169650.9214231 8.0 dB 0.3981072 0.9290819 8.5 dB 0.3758374 0.9360712 9.0 dB0.3548134 0.9424353 9.5 dB 0.3349654 0.9482180 10.0 dB  0.31622780.9534626

That is, the power normalizer 810 corresponds to the normalizing factor,and reduces the power of the multiplexed signal by an amount by whichthe combiner 340 has increased the power.

In this case, each of the normalizing factor and the scaling factor maybe a rational number larger than 0 and smaller than 1.

In this case, the scaling factor may decrease as a reduction in powercorresponding to the injection level controller 330 becomes larger, andthe normalizing factor may increase as a reduction in powercorresponding to the injection level controller 330 becomes larger.

The power normalized signal passes through the time interleaver 350 fordistributing burst errors occurring over a channel, and is transmittedvia the OFDM transmitter robust to multi-path and Doppler phenomena.

In this case, it can be seen that the time interleaver 350 performsinterleaving that is applied to both the core layer signal and theenhanced layer signal. That is, the core layer and the enhanced layershare the time interleaver, thereby preventing the unnecessary use ofmemory and also reducing latency at the receiver.

Although will be described later in greater detail, the enhanced layersignal may correspond to enhanced layer data restored based oncancellation corresponding to the restoration of core layer datacorresponding to the core layer signal. The combiner 340 may combine oneor more extension layer signals having power levels lower than those ofthe core layer signal and the enhanced layer signal with the core layersignal and the enhanced layer signal.

FIG. 9 is a block diagram illustrating still another example of thesignal multiplexer illustrated in FIG. 1.

Referring to FIG. 9, it can be seen that a signal multiplexermultiplexes data corresponding to N (N is a natural number equal to orlarger than 1) extension layers together in addition to core layer dataand enhanced layer data.

That is, the signal multiplexer illustrated in FIG. 9 includes Nextension layer BICM units 410, . . . , 430 and injection levelcontrollers 440, . . . , 460 in addition to a core layer BICM unit 310,an enhanced layer BICM unit 320, an injection level controller 330, acombiner 340, a power normalizer 810, and a time interleaver 350.

The core layer BICM unit 310, enhanced layer BICM unit 320, injectionlevel controller 330, combiner 340 and time interleaver 350 illustratedin FIG. 9 have been described in detail in conjunction with FIG. 3.

Each of the N extension layer BICM units 410, . . . , 430 independentlyperforms BICM encoding, and each of the injection level controllers 440,. . . , 460 performs power reduction corresponding to a correspondingextension layer, thereby enabling a power reduced extension layer signalto be combined with other layer signals via the combiner 340.

In particular, it is preferred that a reduction in power correspondingto each of the injection level controllers 440, . . . , 460 be higherthan a reduction in power of the injection level controller 330. Thatis, a lower one of the injection level controllers 330, 440, . . . , 460illustrated in FIG. 9 may correspond to a larger reduction in power.

In the present invention, power adjustment may be increasing ordecreasing the power of an input signal, and may be increasing ordecreasing the gain of an input signal.

The power normalizer 810 mitigates an increase in power caused by thecombination of a plurality of layer signals by the combiner 340.

The time interleaver 350 performs interleaving equally applied to thesignals of the layers by interleaving the normalized signals.

FIG. 10 is a block diagram illustrating still another example of thesignal demultiplexer illustrated in FIG. 1.

Referring to FIG. 10, a signal demultiplexer according to an embodimentof the present invention includes a time deinterleaver 510, ade-normalizer 1010, core layer BICM decoder 520, an enhanced layersymbol extractor 530, a de-injection level controller 1020, and anenhanced layer BICM decoder 540.

In this case, the signal demultiplexer illustrated in FIG. 10 maycorrespond to the signal multiplexer illustrated in FIG. 8.

The time deinterleaver 510 receives a received signal from an OFDMreceiver for performing operations, such as synchronization, channelestimation and equalization, and performs an operation related to thedistribution of burst errors occurring over a channel.

The de-normalizer 1010 corresponds to the power normalizer of thetransmitter, and increases power by an amount by which the powernormalizer has decreased the power.

Although the de-normalizer 1010 is illustrated as adjusting the power ofthe output signal of the time interleaver 510 in the example illustratedin FIG. 10, the de-normalizer 1010 may be located before the timeinterleaver 510 so that power adjustment is performed beforeinterleaving in some embodiments.

That is, the de-normalizer 1010 may be viewed as being located before orafter the time interleaver 510 and amplifying the magnitude of a signalfor the purpose of the LLR calculation of the core layer symboldemapper.

The output of the time deinterleaver 510 (or the output of thede-normalizer 1010) is provided to the core layer BICM decoder 520, andthe core layer BICM decoder 520 restores core layer data.

In this case, the core layer BICM decoder 520 includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder. The core layer symbol demapper calculates LLR valuesrelated to symbols, the core layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the core layer errorcorrection decoder corrects error occurring over a channel.

In particular, the core layer error correction decoder may output onlyinformation bits, or may output whole bits in which information bitshave been mixed with parity bits. In this case, the core layer errorcorrection decoder may output only information bits as core layer data,and may output whole bits in which information bits have been mixed withparity bits to the enhanced layer symbol extractor 530.

The enhanced layer symbol extractor 530 is provided with the whole bitsby the core layer BICM decoder 520 of the core layer error correctiondecoder, and extracts enhanced layer symbols from the output signal ofthe time deinterleaver 510.

In this case, the enhanced layer symbol extractor 530 includes a buffer,a subtracter, a core layer symbol mapper, and a core layer bitinterleaver. The buffer stores the output signal of the timedeinterleaver 510 or de-normalizer 1010. The core layer bit interleaverreceives the whole bits (information bits+parity bits) of the core layerBICM decoder, and performs the same core layer bit interleaving as thetransmitter. The core layer symbol mapper generates core layer symbols,which are the same as the transmitter, from the interleaved signal. Thesubtracter obtains enhanced layer symbols by subtracting the outputsignal of the core layer symbol mapper from the signal stored in thebuffer, and transfers the enhanced layer symbols to the de-injectionlevel controller 1020.

In this case, the core layer bit interleaver and core layer symbolmapper included in the enhanced layer symbol extractor 530 may be thesame as the core layer bit interleaver and the core layer symbol mapperillustrated in FIG. 8.

The de-injection level controller 1020 receives the enhanced layersymbols, and increases the power of the input signal by an amount bywhich the injection level controller of the transmitter has decreasedthe power. That is, the de-injection level controller 1020 amplifies theinput signal, and provides the amplified input signal to the enhancedlayer BICM decoder 540. For example, if at the transmitter, the powerused to combine the enhanced layer signal is lower than the power usedto combine the core layer signal by 3 dB, the de-injection levelcontroller 1020 functions to increase the power of the input signal by 3dB.

The enhanced layer BICM decoder 540 receives the enhanced layer symbolwhose power has been increased by the de-injection level controller1020, and restores the enhanced layer data.

In this case, the enhanced layer BICM decoder 540 may include anenhanced layer symbol demapper, an enhanced layer bit deinterleaver, andan enhanced layer error correction decoder. The enhanced layer symboldemapper calculates LLR values related to the enhanced layer symbols,the enhanced layer bit deinterleaver strongly mixes the calculated LLRvalues with burst errors, and the enhanced layer error correctiondecoder corrects error occurring over a channel.

That is, the signal demultiplexer illustrated in FIG. 10 restores corelayer data first, leaves only the enhanced layer symbols by cancellationthe core layer symbols in the received signal symbols, and then restoresenhanced layer data by increasing the power of the enhanced layersymbols.

FIG. 11 is a block diagram illustrating still another example of thesignal demultiplexer illustrated in FIG. 1.

Referring to FIG. 11, a signal demultiplexer according to an embodimentof the present invention includes a time deinterleaver 510, ade-normalizer 1010, a core layer BICM decoder 520, an enhanced layersymbol extractor 530, an enhanced layer BICM decoder 540, one or moreextension layer symbol extractors 650 and 670, one or more extensionlayer BICM decoders 660 and 680, and de-injection level controllers1020, 1150 and 1170.

In this case, the signal demultiplexer illustrated in FIG. 11 maycorrespond to the signal multiplexer illustrated in FIG. 9.

The time deinterleaver 510 receives a received signal from an OFDMreceiver for performing operations, such as synchronization, channelestimation and equalization, and performs an operation related to thedistribution of burst errors occurring over a channel.

The de-normalizer 1010 corresponds to the power normalizer of thetransmitter, and increases power by an amount by which the powernormalizer has decreased the power.

Although the de-normalizer 1010 is illustrated as adjusting the power ofthe output signal of the time interleaver 510 in the example illustratedin FIG. 11, the de-normalizer 1010 may be located before the timeinterleaver 510 so that power adjustment is performed beforeinterleaving in some embodiments.

That is, the de-normalizer 1010 may be viewed as being located before orafter the time interleaver 510 and amplifying the magnitude of a signalfor the purpose of the LLR calculation of the core layer symboldemapper.

The output of the time deinterleaver 510 (or the output of thede-normalizer 1010) is provided to the core layer BICM decoder 520, andthe core layer BICM decoder 520 restores core layer data.

In this case, the core layer BICM decoder 520 includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder. The core layer symbol demapper calculates LLR valuesrelated to symbols, the core layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the core layer errorcorrection decoder corrects error occurring over a channel.

In particular, the core layer error correction decoder may output onlyinformation bits, or may output whole bits in which information bitshave been mixed with parity bits. In this case, the core layer errorcorrection decoder may output only information bits as core layer data,and may output whole bits in which information bits have been mixed withparity bits to the enhanced layer symbol extractor 530.

The enhanced layer symbol extractor 530 is provided with the whole bitsby the core layer BICM decoder 520 of the core layer error correctiondecoder, and extracts enhanced layer symbols from the output signal ofthe time deinterleaver 510.

In this case, the enhanced layer symbol extractor 530 includes a buffer,a subtracter, a core layer symbol mapper, and a core layer bitinterleaver. The buffer stores the output signal of the timedeinterleaver 510 or de-normalizer 1010. The core layer bit interleaverreceives the whole bits (information bits+parity bits) of the core layerBICM decoder, and performs the same core layer bit interleaving as thetransmitter. The core layer symbol mapper generates core layer symbols,which are the same as the transmitter, from the interleaved signal. Thesubtracter obtains enhanced layer symbols by subtracting the outputsignal of the core layer symbol mapper from the signal stored in thebuffer, and transfers the enhanced layer symbols to the de-injectionlevel controller 1020.

In this case, the core layer bit interleaver and core layer symbolmapper included in the enhanced layer symbol extractor 530 may be thesame as the core layer bit interleaver and the core layer symbol mapperillustrated in FIG. 9.

The de-injection level controller 1020 receives the enhanced layersymbols, and increases the power of the input signal by an amount bywhich the injection level controller of the transmitter has decreasedthe power. That is, the de-injection level controller 1020 amplifies theinput signal, and provides the amplified input signal to the enhancedlayer BICM decoder 540.

The enhanced layer BICM decoder 540 receives the enhanced layer symbolwhose power has been increased by the de-injection level controller1020, and restores the enhanced layer data.

In this case, the enhanced layer BICM decoder 540 may include anenhanced layer symbol demapper, an enhanced layer bit deinterleaver, andan enhanced layer error correction decoder. The enhanced layer symboldemapper calculates LLR values related to the enhanced layer symbols,the enhanced layer bit deinterleaver strongly mixes the calculated LLRvalues with burst errors, and the enhanced layer error correctiondecoder corrects error occurring over a channel.

In particular, the enhanced layer error correction decoder may outputonly information bits, and may output whole bits in which informationbits have been combined with parity bits. In this case, the enhancedlayer error correction decoder may output only information bits asenhanced layer data, and may output whole bits in which information bitshave been mixed with parity bits to the extension layer symbol extractor650.

The extension layer symbol extractor 650 receives whole bits from theenhanced layer error correction decoder of the enhanced layer BICMdecoder 540, and extracts extension layer symbols from the output signalof the de-injection level controller 1020.

In this case, the de-injection level controller 1020 may amplify thepower of the output signal of the subtracter of the enhanced layersymbol extractor 530.

In this case, the extension layer symbol extractor 650 includes abuffer, a subtracter, an enhanced layer symbol mapper, and an enhancedlayer bit interleaver. The buffer stores the output signal of thede-injection level controller 1020. The enhanced layer bit interleaverreceives the whole bits information (bits+parity bits) of the enhancedlayer BICM decoder, and performs enhanced layer bit interleaving that isthe same as that of the transmitter. The enhanced layer symbol mappergenerates enhanced layer symbols, which are the same as those of thetransmitter, from the interleaved signal. The subtracter obtainsextension layer symbols by subtracting the output signal of the enhancedlayer symbol mapper from the signal stored in the buffer, and transfersthe extension layer symbols to the extension layer BICM decoder 660.

In this case, the enhanced layer bit interleaver and the enhanced layersymbol mapper included in the extension layer symbol extractor 650 arethe same as the enhanced layer bit interleaver and the enhanced layersymbol mapper illustrated in FIG. 9.

The de-injection level controller 1150 increases power by an amount bywhich the injection level controller of a corresponding layer hasdecreased the power at the transmitter.

The extension layer BICM decoder 660 receives the extension layersymbols whose power has been increased by the de-injection levelcontroller 1150, and restores extension layer data.

In this case, the extension layer BICM decoder 660 may include anextension layer symbol demapper, an extension layer bit deinterleaver,and an extension layer error correction decoder. The extension layersymbol demapper calculates LLR values related to the extension layersymbols, the extension layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the extension layer errorcorrection decoder corrects error occurring over a channel.

In particular, each of the extension layer symbol extractor and theextension layer BICM decoder may include two or more extractors ordecoders if two or more extension layers are present.

That is, in the example illustrated in FIG. 6, the extension layer errorcorrection decoder of the extension layer BICM decoder 660 may outputonly information bits, and may output whole bits in which informationbits have been combined with parity bits. In this case, the extensionlayer error correction decoder outputs only information bits asextension layer data, and may output whole bits in which informationbits have been mixed with parity bits to the subsequent extension layersymbol extractor 670.

The configuration and operation of the extension layer symbol extractor670, the extension layer BICM decoder 680 and the de-injection levelcontroller 1170 can be easily understood from the configuration andoperation of the above-described extension layer symbol extractor 650,extension layer BICM decoder 660 and de-injection level controller 1150.

A lower one of the de-injection level controllers 1020, 1150 and 1170illustrated in FIG. 11 may correspond to a larger increase in power.That is, the de-injection level controller 1150 may increase power morethan the de-injection level controller 1020, and the de-injection levelcontroller 1170 may increase power more than the de-injection levelcontroller 1150.

It can be seen that the signal demultiplexer illustrated in FIG. 11restores core layer data first, restores enhanced layer data using thecancellation of core layer symbols, and restores extension layer datausing the cancellation of enhanced layer symbols. Two or more extensionlayers may be provided, in which case restoration starts with anextension layer combined at a higher power level.

FIG. 12 is an operation flowchart illustrating a signal multiplexingmethod according to an embodiment of the present invention.

Referring to FIG. 12, in the signal multiplexing method according to thepresent embodiment, BICM is applied to core layer data at step S1210.

Furthermore, in the signal multiplexing method according to the presentembodiment, BICM is applied to enhanced layer data at step S1220.

The BICM applied at step S1220 may be different from the BICM applied tostep S1210. In this case, the BICM applied at step S1220 may be lessrobust than the BICM applied to step S1210. In this case, the bit rateof the BICM applied at step S1220 may be less robust than that of theBICM applied to step S1210.

In this case, an enhanced layer signal may correspond to the enhancedlayer data that is restored based on cancellation corresponding to therestoration of the core layer data corresponding to a core layer signal.

Furthermore, in the signal multiplexing method according to the presentembodiment, a power-reduced enhanced layer signal is generated byreducing the power of the enhanced layer signal at step S1230.

In this case, at step S1230, an injection level may be changed from 3.0dB to 10.0 dB in steps of 0.5 dB.

Furthermore, in the signal multiplexing method according to the presentembodiment, a multiplexed signal is generated by combining the corelayer signal and the power-reduced enhanced layer signal at step S1240.

That is, at step S1240, the core layer signal and the enhanced layersignal are combined at different power levels so that the power level ofthe enhanced layer signal is lower than the power level of the corelayer signal.

In this case, at step S1240, one or more extension layer signals havinglower power levels than the core layer signal and the enhanced layersignal may be combined along with the core layer signal and the enhancedlayer signal.

Furthermore, in the signal multiplexing method according to the presentembodiment, the power of the multiplexed signal is reduced at stepS1250.

In this case, at step S1250, the power of the multiplexed signal may bereduced to the power of the core layer signal. In this case, at stepS1250, the power of the multiplexed signal may be reduced by an amountby which the power has been increased at step S1240.

Furthermore, in the signal multiplexing method according to the presentembodiment, interleaving applied to both the core layer signal and theenhanced layer signal is performed at step S1260.

The signal multiplexing method illustrated in FIG. 12 may correspond tosteps S240 and S250 illustrated in FIG. 2.

As described above, with respect to the signal multiplexing apparatusand method according to the present invention, the configurations andoperations of the above-described embodiments are not restrictivelyapplied, but all or some of the embodiments may be selectively combinedand configured so that the embodiments may be modified in various ways.

1. A broadcast signal reception apparatus, comprising: an antennaconfigured to receive an OFDM signal transmitted from a transmitter, theOFDM signal corresponding to a multiplexed signal; an OFDM receiverconfigured to generate a received signal by performing any one or anycombination of any two or more of synchronization, channel estimationand equalization; a time deinterleaver configured to perform timedeinterleaving on the received signal; a core layer BICM decoderconfigured to restore core layer data of the multiplexed signal; anenhanced layer symbol extractor configured to extract enhanced layersymbols by performing cancellation corresponding to the core layer data;and an enhanced layer BICM decoder configured to restore enhanced layerdata corresponding to the enhanced layer symbols, wherein the core layerdata corresponds to a core layer and the enhanced layer data correspondsto an enhanced layer.
 2. The broadcast signal reception apparatus ofclaim 1, wherein the core layer BICM decoder includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder.
 3. The broadcast signal reception apparatus of claim1, wherein the enhanced layer BICM decoder includes an enhanced layersymbol demapper, an enhanced layer bit deinterleaver, and an enhancedlayer error correction decoder.
 4. The broadcast signal receptionapparatus of claim 1, wherein the multiplexed signal corresponds to acombination of a core layer signal and a power-reduced enhanced layersignal.
 5. The broadcast signal reception apparatus of claim 4, whereinthe power-reduced enhanced layer signal is generated corresponding to ascaling factor from an enhanced layer signal and the power of themultiplexed signal is reduced corresponding to a normalizing factor inthe transmitter.
 6. The broadcast signal reception apparatus of claim 5,wherein the scaling factor decreases as a reduction in powercorresponding to the power-reduced enhanced layer signal becomes larger,and the normalizing factor increases as the reduction in power becomeslarger.
 7. The broadcast signal reception apparatus of claim 1, furthercomprising: a de-normalizer configured to increase the power of an inputsignal by a level corresponding to a reduction in power by a powernormalizer of the transmitter to generate a power-adjusted signal; andwherein the power normalizer corresponds to a normalizing factor, andreduces the power of a multiplexed signal by an amount by which thepower has been increased by a combiner of the transmitter.
 8. Thebroadcast signal reception apparatus of claim 1, further comprising: ade-injection level controller configured to increase the power of theenhanced layer symbols by a level corresponding to a reduction in powerby an injection level controller of the transmitter.
 9. The broadcastsignal reception apparatus of claim 8, wherein the injection levelcontroller changes an injection level with one of predetermined stepsizes, the step sizes including 0.5 dB.
 10. The broadcast signalreception apparatus of claim 1, wherein the core layer BICM decoder andthe enhanced layer BICM decoder performs operation after the timedeinterleaving which is shared for both a core layer and an enhancedlayer.
 11. A broadcast signal reception method, comprising: receiving anOFDM signal transmitted from a transmitter, the OFDM signalcorresponding to a multiplexed signal; generating a received signal byperforming any one or any combination of any two or more ofsynchronization, channel estimation and equalization; performing timedeinterleaving on the received signal; restoring, by a core layer BICMdecoder, core layer data of the multiplexed signal; extracting enhancedlayer symbols by performing cancellation corresponding to the core layerdata; and restoring, by an enhanced layer BICM decoder, enhanced layerdata corresponding to the enhanced layer symbols, wherein the core layerdata corresponds to a core layer and the enhanced layer data correspondsto an enhanced layer.